Jovan Aleksić

The Gaia DR2 reference frame should be without relative rotation to the quasars (QSOs) and consistent with the International Celestial Reference System (ICRS). For the faint part of DR2 (stars with Gaia magnitude G ≥ 16) that task was done via Gaia's observations of QSOs (G ≥ 17 mag), but the bright DR2 (G ≤ 13 mag) is difficult to validate and it rotates relative to the faint DR2 at rate of the order of 0.1 mas/yr. Very bright DR2 stars (G ≤ 6 mag) mostly have inferior astrometry. Here, the aim is to determine two spin components (ωX and ωY) of the bright DR2 using International Latitude Service (ILS, for 387 stars) and independent latitude stations (INDLS, for 682 stars) catalogs of proper motion in declination γδ; both are referred to the Hipparcos reference frame and their stars are mostly from 4 to 8 mag in the V-band (critical part of DR2). Also, using the new Hipparcos (NHIP) values γδ for ILS and INDLS stars, we can see that the merit of the ILS and INDLS is the long time baseline (Δt ≈ 90 years) important for γδ because the standard deviation of γδ is opposite to Δt. Applying the least squares method (LSM) to the differences of γδ between two catalogs (ILS-DR2, INDLS-DR2, etc.), our results support the mentioned spin. The 3σ criterion and Tukey's fences method were used to reject some stars, the Abbe criterion to explain the variability in ILS-DR2 and other γδ differences, and the Shapiro-Wilk test to check the standard distribution of differences. The obtained ωY is significant at the 2 σ level, and the ILS and INDLS catalogs could be useful for validation of the bright reference frame of Gaia DR2.

Large Synoptic Survey Telescope will make great contributions to many scientific fields. One of the modules will be time-domain astronomy and detection of transient events. In this paper, some considerations about transient events and alerts are presented.

We present simulator of alerts for the Large Synoptic Survey Telescope (LSST) developed by Belgrade group. This simulator will be used in testing the functionality of external event brokers/Complex Event Processing (CEP) engines. It is based on current LSST Simulation framework and allows for different classes of objects to be ‘alerted’. A Web service based on our simulator is prototyped and can be accessed by developers of brokers/CEP engines.

The work on SerVO - Serbian virtual observatory (http://servo.aob.rs/~darko) started in 2008, with aims 1) To establish SerVO and join the EuroVO - European Virtual Observatory and IVOA - Inetrnational Virtual Observatory Alliance; 2) To create SerVO data Center for digitalization and archiving in VO format photo-plates from Belgrade Astronomical Observatory and other astronomical results obtained by the staff; 3) To develop the tools for visualization of data; 3) To develop together with Observatoire de Paris, STARK-B - database containing as the first step Stark widths and shifts of spectral lines, determined within the semiclassical perturbation approach by two of us (MSD-SSB) and to create a mirror site in Belgrade; 4) To make a mirror site for DSED (Darthmouth Stellar Evolution Database) in which development took part one of us (DJ). An additional aim is the creation of VAMDC (Virtual Atomic and Molecular Data Center) AOB (Astronomical Observatory of Belgrade) Node, and a recent objective is the collaboration with the Large Synoptic Telescope (LSST) project. In this contribution SerVO project is reviewed within the context of e-science in Astronomy -- Astroinformatics.